antispasmodics

 The muscle relaxants listed can be divided into antispasmodic agents (primarily for musculoskeletal pain) and antispasticity agents (for spasticity from upper motor neuron lesions). Comparative efficacy is generally similar, with choice guided by side effect profiles, abuse potential, and comorbidities. Below is a concise summary of the pros, cons, risks, and recommended doses for each agent, with a comparison of benefits and risks.

Comparison: For acute musculoskeletal pain, cyclobenzaprine, methocarbamol, metaxalone, and orphenadrine have similar efficacy, with cyclobenzaprine being most sedating and carisoprodol having the highest abuse risk. For spasticity, baclofen and tizanidine are preferred, with tizanidine causing more dry mouth and baclofen more weakness. Dantrolene and chlorzoxazone carry rare but serious hepatotoxicity risks. Benzodiazepines (diazepam, clonazepam) are not recommended for routine use due to dependence risk and lack of superior efficacy. Neuromuscular blockers (atracurium, etc.) and botulinum toxin are not used for routine musculoskeletal pain or generalized spasticity in ambulatory settings.[1-3][5]

The U.S. Department of Veterans Affairs and Department of Defense recommend against routine use of skeletal muscle relaxants for acute low back pain due to limited benefit and established harms.[6] The American Academy of Pediatrics notes that benefits are limited to short-term use (3–7 days), with no evidence for long-term efficacy and significant CNS side effects.[7]

Drug (Brand)

Typical Dose (Adults)

Pros/Benefits

Cons/Risks/Adverse Effects

Key Comparative Points

References

Cyclobenzaprine (Fexmid)

5–10 mg TID (max 30 mg/day)

Well-studied, effective for acute musculoskeletal pain

Sedation, dry mouth, anticholinergic effects, avoid in elderly

Most sedating, not superior to others

[1-4]

Methocarbamol

1.5 g QID (max 8 g/day)

Less sedating, low abuse potential

Drowsiness, dizziness, GI upset

Less sedating than cyclobenzaprine

[2, 5]

Carisoprodol

250–350 mg TID and HS

Effective for acute pain

Abuse/dependence risk, sedation, withdrawal

High abuse potential, not preferred

[2-3, 6]

Baclofen

5 mg TID, titrate to 80 mg/day

Effective for spasticity

Weakness, sedation, withdrawal risk

Preferred for spasticity, not pain

[1, 5]

Chlorzoxazone (Lorzone)

250–750 mg TID–QID

Some efficacy for muscle spasm

Hepatotoxicity (rare), sedation

Rare hepatotoxicity

[1-2]

Dantrolene

25 mg QD, titrate to 100 mg QID

Effective for spasticity, malignant hyperthermia

Hepatotoxicity (rare), weakness, sedation

Rarely used due to hepatotoxicity

[1, 5]

Metaxalone (Skelaxin)

800 mg TID–QID

Less sedating, low abuse potential

Dizziness, GI upset, rare hepatotoxicity

Less sedating, limited efficacy data

[2-3]

Orphenadrine (Norgesic)

100 mg BID

Some efficacy for acute pain

Anticholinergic effects, sedation

Similar efficacy, more anticholinergic

[1-2]

Tizanidine

2–4 mg up to TID, max 36 mg/day

Effective for spasticity, less weakness

Sedation, hypotension, dry mouth, hepatotoxicity

More dry mouth, less weakness than baclofen

[1, 5]

Diazepam

2–10 mg TID–QID

Effective for spasticity, anxiety

Sedation, dependence, cognitive impairment

Not superior for pain, abuse risk

[1][2, 5]

Atracurium, Alcuronium, Cisatracurium, Succinylcholine

IV only, per anesthesia protocols

Used for paralysis in anesthesia/ICU

Respiratory paralysis, requires ventilation

Not for musculoskeletal pain/spasticity

[5]

Botulinum toxin type A

Intramuscular, dose varies

Focal spasticity, long duration

Local weakness, rare systemic effects

For focal spasticity only

[5]

Clonazepam

0.5–2 mg BID

Spasticity, anxiety

Sedation, dependence, cognitive impairment

Not first-line for muscle spasm

[5]